The invention relates to the constructional equipment, and more particularly to pneumatic impact mechanisms for driving rod-like members.
The present invention may be most advantageously used for driving earthing electrodes, anchor rods and similar rod-like members having the diameter which is incommensurably small compared to their length, in soil.
Different types of mechanisms for driving rod-like members in soil are known.
Known in the art is a hydraulically-operated mechanism for driving rod-like earthing or ground electrodes in soil. The mechanism comprises a hydraulic power cylinder having a piston with a hollow piston rod on either side thereof for receiving the electrode to be driven. The upper portion of the cylinder accommodates a guide coaxial with the rod, the guide having a large-pitch helical slot along the entire height thereof. A pin received in the helical slot of the guide is secured to the outer periphery of the piston rod. A self-locking clamp is mounted at the lower, free end of the piston rod. The casing of the power cylinder is secured to an electric transmission line support or to a frame of a constructional machine, such as a tractor, by means of collars. Working fluid may be fed either to the upper or lower chamber of the hydraulic cylinder.
During the initial period of operation, the piston rod is lifted to the upper position, and the electrode is inserted therein so as to bear against the soil. Then fluid is admitted to the upper chamber of the power cylinder, and the piston and the piston rod are displaced downwards. The clamp rigidly grips the electrode to cause its displacement together with the piston rod. While moving downwards, the pin is displaced in the helical slot of the guide to impart an additional rotary motion to the electrode. When the piston reaches the lower position, the fluid is fed in the opposite direction, and the piston rod is caused to move upwards. Thus the clamp releases the electrode and is lifted together with the piston rod without the electrode. After the piston rod reaches the upper position, it starts driving the electrode anew.
The disadvantages of the prior art hydraulically driven mechanism consist in its large size, the need in securing to a massive support or frame of a machine. In addition, it is difficult to drive a rod in compact and frozen soils by using such mechanism because of the static nature of load application to the rod.
Known in the art is also a pneumatic impact tool for driving rod-like members in soil.
The tool comprises a casing having a clamp rigidly secured to the front end portion thereof. The casing accommodates a reciprocating stepped hammer piston. The rear end portion of the casing is sealed by a tail portion having ports for admitting and discharging air. The stepped hammer piston defines a front end work chamber with the casing and a rear end work chamber with the tail portion. The rear end work chamber is in permanent communication with a compressed air source, and the front end work chamber communicates with the rear end work chamber and with atmosphere at regular intervals.
The tool is secured at the top of a rod by means of the clamp. Upon feeding compressed air, the stepped hammer piston reciprocates to deliver blows to the front end portion of the casing. The rod is driven in soil under the action of these blows transmitted thereto through the casing and clamp.
The prior art tool provides for delivery of blows to the end fact of the rod only, so that rods having the cross-sectional dimensions incommensurably small compared to the length thereof cannot be driven due to their deformation during the driving.
Known in the art is also a pneumatic impact mechanism (U.S. Pat. No. 692,388) comprising a hollow cylindrical casing having a tail portion and a front end portion, the casing accommodating a reciprocating stepped hammer piston. The hammer piston defines a variable volume rear end work chamber in the casing on the tail portion side in permanent communication with a compressed air source, and a variable volume front end work chamber on the front end portion side. The front end work chamber communicates, at regular intervals with the rear end work chamber when the stepped hammer piston is in the front end position and with atmosphere, via an axial passage of the hammer piston and radial bores in the periphery of the small-diameter portion of the stepped hammer piston cooperating with the tail portion, when the hammer piston is in the rear end position. The stepped hammer imparts blows to the casing during reciprocations under the action of compressed air admitted to the work chambers.
The stepped hammer piston reciprocates due to the difference in surface areas thereof on the sides of the front end and rear end work chambers under compressed air pressure.
During the driving of rod-like members, the impact mechanism is secured to the upper portion of the rod. The rod is driven in soil under the action of blows imparted to the end face thereof. Thus, this prior art mechanism cannot be used for driving rods having the cross-sectional dimensions incommensurably smaller compared to the length thereof due to their deformation during the driving.